Sometimes schools will allow the child to chew gum or suck on hard candies (sugarless, of course) as part of a 504 plan or IEP. My son had a 'squeezy apple' in 2nd grade, and the teacher was very upset that he poked many holes into it with his pencils and basically destroyed it. I asked DS if he couldn't just squeese it, and he said that he had so much anger inside that squeezing wasn't enough. Ah, 2nd grade! That was his worst years ever.
I think that there are therapudic clays that are a bit like silly putty that might help. Also clear tube pencil toppers for chewing. you can browse:
www.southpawenterprises.com I like the idea of a bead on a leather strap or key chain for some discrete chewing or fingering.
BTW here are some books that 'cheer one on' when the task is negotiation with a difficult child:
Ross W Greene The Explosive Child
and
http://www.thinkingpreteen.com/myrnashure.htmI know it isn't easy!
Smiles,
Grinity
